[
https://issues.apache.org/jira/browse/MAPREDUCE-4485?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Colin Patrick McCabe updated MAPREDUCE-4485:
--------------------------------------------
Description:
container-executor.c contains the following code:
{code}
fclose(stdin);
fflush(LOGFILE);
if (LOGFILE != stdout) {
fclose(stdout);
}
if (ERRORFILE != stderr) {
fclose(stderr);
}
if (chdir(primary_app_dir) != 0) {
fprintf(LOGFILE, "Failed to chdir to app dir - %s\n", strerror(errno));
return -1;
}
execvp(args[0], args);
{code}
Whenever you open a new file descriptor, its number is the lowest available
number. So if {{stdout}} (fd number 1) has been closed, and you do
open("/my/important/file"), you'll get assigned file descriptor 1. This means
that any printf statements in the program will be now printing to
/my/important/file. Oops!
The correct way to get rid of stdin, stdout, or stderr is not to close them,
but to make them point to /dev/null. {{dup2}} can be used for this purpose.
It looks like LOGFILE and ERRORFILE are always set to stdout and stderr at the
moment. However, this is a latent bug that should be fixed in case these are
ever made configurable (which seems to have been the intent).
was:
container-executor.c contains the following code:
{code}
fclose(stdin);
fflush(LOGFILE);
if (LOGFILE != stdout) {
fclose(stdout);
}
if (ERRORFILE != stderr) {
fclose(stderr);
}
if (chdir(primary_app_dir) != 0) {
fprintf(LOGFILE, "Failed to chdir to app dir - %s\n", strerror(errno));
return -1;
}
execvp(args[0], args);
{code}
Whenever you open a new file descriptor, its number is the lowest available
number. So if {{stdout}} (fd number 1) has been closed, and you do
open("/my/important/file"), you'll get assigned file descriptor 1. This means
that any printf statements in the program will be now printing to
/my/important/file. Oops!
The correct way to get rid of stdin, stdout, or stderr is not to close them,
but to make them point to /dev/null. {{dup2}} can be used for this purpose.
Another thing we should be doing in container-executor.c is closing any file
descriptors we don't need. Because container-executor was forked off of the
JVM, any file that was open at the time the JVM called fork() will also be open
for us. These FDs will continue to be open even after the {{execve}}, unless
we close them manually. This could be both a resource leak and a security
breach.
Target Version/s: 2.0.1-alpha
Affects Version/s: 2.0.1-alpha
Summary: container-executor should deal with stdout, stderr
better (was: container-executor should deal with file descriptors better)
> container-executor should deal with stdout, stderr better
> ---------------------------------------------------------
>
> Key: MAPREDUCE-4485
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4485
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: nodemanager
> Affects Versions: 2.0.1-alpha
> Reporter: Colin Patrick McCabe
> Priority: Minor
>
> container-executor.c contains the following code:
> {code}
> fclose(stdin);
> fflush(LOGFILE);
> if (LOGFILE != stdout) {
> fclose(stdout);
> }
> if (ERRORFILE != stderr) {
> fclose(stderr);
> }
> if (chdir(primary_app_dir) != 0) {
> fprintf(LOGFILE, "Failed to chdir to app dir - %s\n", strerror(errno));
> return -1;
> }
> execvp(args[0], args);
> {code}
> Whenever you open a new file descriptor, its number is the lowest available
> number. So if {{stdout}} (fd number 1) has been closed, and you do
> open("/my/important/file"), you'll get assigned file descriptor 1. This
> means that any printf statements in the program will be now printing to
> /my/important/file. Oops!
> The correct way to get rid of stdin, stdout, or stderr is not to close them,
> but to make them point to /dev/null. {{dup2}} can be used for this purpose.
> It looks like LOGFILE and ERRORFILE are always set to stdout and stderr at
> the moment. However, this is a latent bug that should be fixed in case these
> are ever made configurable (which seems to have been the intent).
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
